Health risks associated with polycarbonate plastics have users taking a closer look at these popular water bottles

Highly durable and lightweight, resistant to stains and odors, and able to withstand extremes of hot and cold, screw-cap Nalgene bottles are marketed as an environmentally responsible substitute for disposable water bottles. While different models of Nalgene water bottles utilize different plastics in their composition; the popular Nalgene Lexan bottles are made of polycarbonate plastic. These bottles are identified by the #7 recycling symbol (although not all #7 plastics are polycarbonate).

Polycarbonate plastic (PC) offers the benefits of durability and heat-resistance, but it is also a plastic known to leach the hormone-disrupting chemical bisphenol-A (BPA).

Concerns about the presence of BPA in water bottles' construction have led some retailers to remove polycarbonate containers made by Nalgene and other manufacturers from store shelves. But while here is little dispute that BPA can disrupt the hormonal system, scientists differ markedly on whether the low doses found in food and beverage containers can be harmful.

Are these bottles safe or not?

It should be noted that there have been no scientific studies which specifically link Nalgene Lexan water bottles to unsafe leaching of BPA. However, because these bottles are made of polycarbonate, their chemical composition suggests a connection.

In 2003, a study, published in Environmental Health Perspectives (EHP), confirmed earlier studies of baby bottles which found that while new bottles contained residual amounts of BPA, these amounts decreased dramatically after a short period of use. However, after repeated washings and scrubbings, the levels of BPA leaching from the bottles increased significantly. The study concludes, "The increased migration levels may be due to polymer degradation."

An expert panel of 38 academic and government researchers who attended a National Institutes of Health-sponsored conference in August 2007, said in a study that "the potential for BPA to impact human health is a concern, and more research is clearly needed." In response, the FDA stated: "BPA has been used in consumer products for over 50 years. In that time, there has been no evidence that BPA is harmful to humans, either as the result of dietary intake or industrial worker exposures."

So the degree of BPA leaching from PC water bottles, and its associated health risks, is still a matter of debate. However, it is safe to say that with PC water bottles, such as the Nalgene Lexan bottles, care should be taken to limit polymer degradation.Care of Nalgene water bottles

The following simple measures can be taken to minimize any potential health risks associated with Nalgene bottles.

• wash new PC water bottles before using• wash bottles by hand with a mild detergent; do not wash in dishwashers• avoid using bleach or strong detergents when washing• keep bottles out of direct sunlight and away from other heat sources• replace old bottles which appear faded, worn or crazed• never use PC bottles in a microwave• use PC bottles for cold water only,and not for hot beverages

Alternatives to Nalgene water bottles

The Nalgene Lexan water bottle is popular because it's both durable and lightweight. The following water bottles currently available on the market have one or both of these qualities, but perhaps to a lesser degree. However, these bottles do not have the BTA leaching concerns currently associated with bottles constructed with polycarbonate plastic.

• Stainless Steel - reusable, lightweight bottles are made of stainless steel inside and out. Stainless steel doesn't leach or react, but avoid freexing or filling with hot water. A popular supplier is Klean Kanteen.

• Glass - pose no health risks, but have the obvious disadvantage of being breakable.

• Polypropylene - look for bottles made of #5 PP (polypropylene), such as Rubbermaid's Chuggables

• HDPE (Polyethylene) - look for bottles made of #2 HDPE (high density polyethylene), or a #4 LDPE (low density polyethylene). HDPE is a softer opaque plastic made from petroleum. Scientists and health advocates have reported no known problems with HDPE. Nalgene makes bottles of this material.

• Enamel coated aluminum - Sigg is a popular supplier

• Corn-based - these reusable bottles use no plastic or petroleum based materials. more info

The type of plastic bottle in which water is usually sold is usually a #1, and is only recommended for one time use. #1 PET or PETE bottles (polyethylene terephthalate) may leach DEHA, a known carcinogen, if used more than once. Better to use a reusable water bottle, and fill it with your own filtered water from home and keep these single-use bottles out of the landfill.